In line with the Vision Research Plan objectives of developing noninvasive techniques to "improve the prevention, diagnosis, and management of retinal disease," we propose to develop and test a new method to noninvasively measure the thickness of the retina and nerve fiber layer. When performed across the macula, the measurement of retinal thickness can be clinically important in conditions such as macular edema, which is associated with an increased retinal thickness, and macular atrophy, which is associated with retinal thinning. Around the optic nervehead, the measurement can be usefel in cases of increased tissue thickness such as seen in papilledema. Also, since the nerve fibers compose a major portion of the retinal tissue at the disc edge, the measurement of thickness can provide a sensitive and accurate follow up of gradual nerve fiber loss in conditions such as glaucoma and optic nerve atrophies. We propose to develop a method, based on slit-lamp biomicroscopy, capable of providing quantitative measurements of retinal thickness. The incoherent white illumination is replaced by a laser and is thus coherent and monochromatic, and the subjective viewing is substituted by an optoelectronic system. The laser beam scans the fundus along a line, and a thickness profile is obtained in less time than required for an eye movement. Simultaneously, TV frames are acquired to record and display the exact location of each profile. Profiles can be obtained across the macula and at different quadrants around the optic nervehead and radially along the nerve fibers so that the method has potential applications to the clinical conditions mentioned above. Our prior feasibility studies performed with a bence prototype and with an in vitro model indicated that transparent materials 180 to 500 micrometers thick can be measured with a reproducibility of 9 micrometers or better and an accuracy better than 5 micrometers. Theoretical estimates based on experimental data suggested that comparable results can be obtained in human eyes in 200 milliseconds with a laser intensity that is safe for 120 seconds of continuous viewing. We propose now to extend our studies to actual measurements in normal and diseased human eyes. The instrument will be developed in three consecutive phases. It will be tested at each phase in a model eye, animal eyes, and human volunteers. The method will then be used in preliminary studies of selected pathologic conditions involving variations of thickness in the retina and the nerve fiber layer and the thickness will be correlated with ophthalmoscopic and visual field findings.